The term “corneal disease” covers the variety of conditions that affect the cornea, the clear outer layer of the eye. The cornea can often repair itself after injury or disease, but more serious conditions — infections, degenerative diseases, deterioration — need treatment.
The term “corneal disease” refers to a variety of conditions that affect mainly the cornea. These include infections, degenerations, and many other disorders that may arise mostly as a result of heredity.
Along with the sclera (white of the eye), the cornea serves as a barrier against dirt, germs and other particles that can harm the eye’s delicate components. The cornea also filters out some amounts of the sun’s ultraviolet light.
The cornea also plays a key role in vision. As light enters the eye, it’s refracted, or bent, by the outside shape of the cornea. The curvature of this outer layer helps determine how well your eye can focus on objects close up and far away. If the cornea becomes damaged through disease, infection or injury, the resulting scars or discoloration can interfere with vision by blocking or distorting light as it enters the eye.
The three main layers of the cornea are:
With its ability for quick repair, the cornea usually heals after most injury or disease. However, when there is deep injury to the cornea, the healing process may be prolonged, possibly resulting in a variety of symptoms, including:
If you experience any of these symptoms, make an appointment to see an ophthalmologist (eye doctor). They may find a more serious problem or a condition that requires special treatment.
This is an inflammation of the cornea that sometimes occurs with infection after bacteria or fungi enter the cornea. These microorganisms can enter the eye after deep injury, causing infection, inflammation and ulceration of the cornea. Though uncommon, this type of infection can also arise after injury from wearing contact lenses.
Symptoms of keratitis include:
Treatment usually includes antibiotic or antifungal eye drops.
This is a viral infection of the eye that may reoccur (return). The main cause of ocular herpes is the herpes simplex virus I (HSV I). This is the same virus that causes cold sores, but ocular herpes can also result from the sexually transmitted herpes simplex II virus (HSV II) that causes genital herpes.
Ocular herpes produces sores on the surface of the cornea that can lead to scarring and reduced vision. The inflammation can spread deeper into the cornea and eye.
There is no cure for ocular herpes, but it can often be controlled with the use of antiviral drugs.
Shingles is a recurrence (return) of the chickenpox virus in people who have already had the disease. After the bout of chickenpox, this virus usually remains inactive within the nerves of the body. It can later travel down these nerves, infecting specific parts of the body, like the eye. Herpes zoster can cause blisters or lesions on the cornea, fever and pain from affected nerve fibers.
Corneal lesions usually heal by themselves, but antiviral treatment may shorten the course of disease. Some people develop chronic inflammation of the cornea after shingles requiring use of long-term eye drops, or less commonly, corneal surgery.
Shingles can occur in anyone exposed to the chickenpox virus, but there’s an increased risk in older adults (especially those over age 65) and people with a weakened immune system.
See your ophthalmologist if you have any symptoms of shingles near or in the eye.
There are more than 20 corneal dystrophies, diseases that cause structural problems with the cornea. Some of the most common are:
Keratoconus is a progressive disease in which the cornea thins and changes shape. Keratoconus changes the curvature of the cornea, creating either mild or severe distortion, called irregular astigmatism and usually nearsightedness. Keratoconus may also cause swelling and scarring of the cornea and vision loss.
Causes of keratoconus include:
At first, the condition is correctable with glasses or soft contact lenses. But, as the disease progresses, you may need to wear rigid gas permeable contact lenses.
A corneal transplantation may also be necessary. During this procedure, the damaged cornea is replaced with a donated cornea. This operation is successful in about nine out of 10 people with advanced keratoconus. Even after a transplant, you most likely will need glasses or contact lenses to see clearly.
Corneal crosslinking is a newer treatment for keratoconus which uses a special type of ultraviolet light to activate riboflavin eye drops placed on the cornea. This can stabilize the cornea and slow the progression of disease. Your doctor may recommend an evaluation for this treatment if you are a candidate for this therapy.
Map-dot-fingerprint dystrophy is a corneal condition which causes abnormal folds and reduplications of the epithelium, the outermost layer of the cornea. The effects of these changes are patterns in the cornea that resemble maps, dots and small fingerprints.
Map-dot-fingerprint dystrophy usually affects adults between the ages of 40 and 70, or children as a result of heredity. It is usually painless and causes no vision loss. In some cases, however, epithelial erosions may occur. Epithelial erosions are spontaneous corneal abrasions that occur, exposing the nerves lining the cornea and causing severe pain. The cornea’s normal curvature may be altered, causing astigmatism and nearsightedness.
As the cornea is altered, vision may be blurry and accompanied by:
Most patients with this condition require no treatment. If erosions are occurring, they may be managed with topical lubricating ointments, special contact lenses or a minor surgical procedure to debride (remove) the abnormal surface tissue.
Fuch’s dystrophy is a gradual deterioration of the innermost layer of the cornea, the corneal endothelium. This layer acts as a fluid pump to remove excess water from the cornea, maintaining corneal clarity.
As these cells weaken over time, the cornea may swell causing blurred vision. In the advanced stages of this condition, haze and small blisters on the corneal surface may appear, causing pain and irritation.
A slowly progressing disease, the earliest signs of Fuch’s dystrophy may be visible in patients in their 30s and 40s. However, the disease doesn’t normally affect vision until about 20 years later. It is more common in women than men.
Some patients with Fuch’s dystrophy experience blurred vision in the morning that gradually clears up during the day. As the disease worsens, swelling becomes more consistent and vision may be blurry at all times.
Treatment includes:
Lattice dystrophy is characterized by the presence of abnormal protein fibers throughout the stroma. Although this condition can occur at any age, early changes can be seen in childhood.
Lattice dystrophy gets its name from the clear overlapping lines of proteins in the stroma. This can make the cornea cloudy and reduce vision. In some people, these proteins may cause epithelial erosion.
Treatment of lattice dystrophy includes:
Although the early results of corneal transplantation are typically very good, lattice dystrophy may reappear in transplant patients requiring long-term treatment.
Corneal disease can only be diagnosed after a thorough examination by an ophthalmologist
The risk of infectious corneal disease caused by bacteria and viruses can be reduced by protecting the eye from injury and limiting physical contact with people who have contagious forms of conjunctivitis. Avoid sharing eye makeup, contact solution, lens cases and eye drops with people who are infected. Wash your hands thoroughly with soap and warm water for at least 15 seconds after contact with an infected person.